Could it be in the classroom we had a talk last night you left your keys?A. that; whereB.

问题补充：

Could it be in the classroom we had a talk last night you left your keys?

A. that; where

B. in which; where

C. where; that

D. where; in which

答案：

A. that; where

B. in which; where

(答案→)C. where; that

D. where; in which

解析：考查强调句与定语从句的混合使用。第二个为强调句的后半部分，可以通过去掉it could be 和that来验证；第二格先行词在定语从句中作地点状语，故用where。选C。